Rents have risen as incomes stagnated making Baltimore housing less affordable for many.

Stagnant wages and rising rents have created a "double crisis" in Baltimore, where more than half of the city's renters live in housing considered unaffordable, a new report says.

Many of the families struggling to pay rent are poor, but costs also have increased sharply for a growing number of working- and middle-class renters, according to the report for the Abell Foundation, which looked at data from the American Community Survey and American Housing Survey.

Nearly 30 percent of Baltimore's renter families earning between $40,000 and $75,000 a year spend more than 30 percent of their income for housing, considered the standard for affordability. That's up from about 7 percent in 1998 and 11 percent in 2007, according to the report.

"There is this emergent trend within the midmarket, where they can live," said the report's author, Phil M.E. Garboden, a Johns Hopkins University graduate student. "Those families are becoming increasingly burdened."

Middle-income households remain a small part of the rental market in Baltimore, where more than a third of renter families live below the poverty line, yet more and more people are being priced out of affordable housing.

The trend is similar to patterns seen across the country, where the number of renters has outstripped supply of homes, even as incomes remain largely static.

"That's what's pinching middle-income households the most … that they're seeing household costs go up at the same time their incomes haven't kept pace," said Jonathan Spader, senior research associate at the Joint Center for Housing Studies at Harvard University.

Nationally, about 50 percent of renters spend more than 30 percent of their income on housing, while about 26 percent put more than half toward housing, according to the center.

The affordability problem is more acute in Baltimore, where about 57 percent of renters spend more than 30 percent of their income on housing, while about a third spend more than half, the Abell Foundation found.

Female-headed households in Baltimore are especially burdened, as they need more space for children but don't necessarily have larger incomes, the report found. Black households also typically face more affordability problems than white households in Baltimore.

"While wages are remaining stagnant, housing costs are going up everywhere," said Rachel Kutler, leadership organizer with United Workers. "We see it all over."

Rising rent and utility bills led Michael Coleman, 39, to move his family three times in five years, staying with relatives between rentals, he said. The problem became especially bad after his car broke down and he lost his job, which required a vehicle, he said.

Their current home, in Mount Washington, costs about $1,200 a month — a rate only manageable because he and his partner found jobs at United Workers. Still, he said, they live paycheck to paycheck.

"We're crossing our fingers," he said. "There's always that fear."

Economists said one source of the problem is the local job market, where growth is divided between high-paying fields, such as cybersecurity, and low-paying industries, such as the service sector, which account for many of the jobs created since the recession.

The average hourly earnings of private-sector workers in Baltimore was $27.06 last year — more than $3 lower than it was in 2007, when adjusted for inflation.

"The quality of the jobs being created aren't those … that we lost during the recovery," said Daraius Irani, economist at Towson University's Regional Economic Studies Institute.

Another contributor to high housing cost is Baltimore's stock of aging rowhouses, which are expensive to maintain. That makes it likely that property owners will charge more for rent than they would for the larger, newer apartment buildings common elsewhere, Garboden said.

The turbulence of the city's housing market, which sees rapid turnover among investor-owned rentals, also means many of the properties carry mortgages, the report found. This can exacerbate the problem, since those landlords are often less flexible when it comes to rental rates, it said.

More apartment buildings have been constructed and are in the works, but many of them cater to the higher end of the market, which does little to alleviate affordability problems, said Anirban Basu, CEO of the Sage Policy Group.

While cheaper rentals might be available in the city's poorer neighborhoods, Garboden said middle-class residents may be less inclined to relocate to those areas, which are often defined along racial and economic lines.

"Those boundaries are pretty strong in the minds of middle-income renters," he said.

For the poorest families in Baltimore, the shortage of homes — while significant — is less severe than in many parts of the country, including nearby counties, a legacy of federal investments in public housing and other housing subsidies, said Erika Poethig, director of Urban Policy Initiatives at the Urban Institute.

But housing vouchers — which can be used whenever a landlord accepts them and offer a subsidy that is determined based on regional income levels and rents — may contribute to affordability problems in some neighborhoods, said Seema D. Iyer, an assistant professor at the University of Baltimore who leads work on an annual report issued each year on the city's demographics.

This year's report showed that high voucher use in a neighborhood is linked to a high percentage of residents spending more than 30 percent of income on housing. For example, in Belair-Edison, which counts about 420 vouchers per 1,000 rental units, 71 percent of residents spend more than 30 percent of their income on housing.

The mismatch may be because landlords try to charge as much as they can under the voucher program, even if it's more than "what the neighborhood would normally command," Iyer said.